In "The President's Run," the final level of the first game, the President (who you have in your car) will periodically say things like "Nice driving!" or "Where we goin', son?" The timing of this is pretty random, so it's possible for him to say "Nice driving!" while you are sliding down a hill upside-down.
Driver: SF has a ton of hilarious conversations when you shift into someone else's car, it would take far too long to list them all, though Tanner scaring a driver's ed instructor shitless(literally) is one of the highlights.
Tanner: "Hold on, thing's are about to get rough!"
Random Teen: "Oh I don't want to miss this!"
As well as getting girlfriends to admit who they've been cheating on.